1. Field of the Invention
This invention relates to a release silicone emulsion composition and a process for preparing it, and particularly to a silicone emulsion composition suited for use in release paper and a process for preparing it.
2. Description of the Prior Art
In general, a variety of release silicone compositions are used for the purpose of preventing adhesion or fixation that may occur between substrates such as paper and plastics, and sticky materials. Presently available as the release silicone compositions are mainly those of solvent types employing organic solvents in a large quantity, but the organic solvents are disadvantageous in that they may cause environmental pollution, so being undesirable from the viewpoint of safety and sanitation, and an expensive apparatus is required for the recovery thereof. Accordingly, what have been sought after are those employing no organic solvents, and one of them is a release silicone composition of an emulsion type, of which known are a condensation type and an addition type depending on the manner of cure reaction. Of these, the emulsion type compositions have been hitherto used, but can be used only for very special purposes because of their greatly disadvantageously short pot life. Known as the addition type compositions known to have a relatively long pot life are those prepared as mixtures of an emulsion comprising organovinylpolysiloxane, a platinum compound, an emulsifying agent and water with an emulsion comprising organohydrogenpolysiloxane, an emulsifying agent and water (Japanese Patent Publication (KOKOKU) No. 53143/1982), those prepared by an emulsification polymerization process (Japanese Unexamined Patent Publication (KOKAI) No. 52160/1979), etc.
However, the addition type release silicone composition described in Japanese Patent Publication (KOKOKU) No. 53143/1982 lacks in fast-curing properties, and also requires emulsification of two kinds of emulsions with use of a homogenizer to make processes complicate. It also has occurred that the resulting cured silicone film brings about insufficient residual adhesive properties of an adhesive when the composition is used to form a release layer of release papers. Also, the addition type release silicone composition described in Japanese Unexamined Patent Publication (KOKAI) No. 52160/1979 intended to improve the residual adhesive properties of the adhesive when the composition of Japanese Patent Publication (KOKOKU) No. 53143/1982 was used, but actually resulted in poor residual adhesive properties of the adhesive and insufficient release properties of the resulting cured silicone film.